Multi-pane electrochromic windows

ABSTRACT

Window units, for example insulating glass units (IGU&#39;s), that have at least two panes, each pane having an electrochromic device thereon, are described. Two optical state devices on each pane of a dual-pane window unit provide window units having four optical states. Window units described allow the end user a greater choice of how much light is transmitted through the electrochromic window. Also, by using two or more window panes, each with its own electrochromic device, registered in a window unit, visual defects in any of the individual devices are negated by virtue of the extremely small likelihood that any of the visual defects will align perfectly and thus be observable to the user.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation of and claims priority to U.S. patentapplication Ser. No. 14/796,819, filed on Jul. 10, 2015 and titled“MULTI-PANE ELECTROCHROMIC WINDOWS,” which is a continuation of U.S.patent application Ser. No. 14/534,059 (now issued as U.S. Pat. No.9,116,410), filed on Nov. 5, 2014 and titled “MULTI-PANE ELECTROCHROMICWINDOWS,” which is a continuation of U.S. patent application Ser. No.14/160,425 (now issued as U.S. Pat. No. 8,908,259), filed on Jan. 21,2014 and titled “MULTI-PANE ELECTROCHROMIC WINDOWS,” which is acontinuation of U.S. patent application Ser. No. 13/619,772 (now issuedas U.S. Pat. No. 8,665,512), filed on Sep. 14, 2012 and titled“MULTI-PANE ELECTROCHROMIC WINDOWS,” which is a continuation of U.S.patent application Ser. No. 12/851,514 (now issued as U.S. Pat. No.8,270,059), filed on Aug. 5, 2010 and titled “MULTI-PANE ELECTROCHROMICWINDOWS;” all of which are hereby incorporated by reference in theirentirety and for all purposes.

FIELD OF INVENTION

The invention relates generally to electrochromic devices, moreparticularly electrochromic windows.

BACKGROUND

Electrochromism is a phenomenon in which a material exhibits areversible electrochemically-mediated change in an optical property whenplaced in a different electronic state, typically by being subjected toa voltage change. The optical property is typically one or more ofcolor, transmittance, absorbance, and reflectance. One well knownelectrochromic material, for example, is tungsten oxide (WO₃). Tungstenoxide is a cathodic electrochromic material in which a colorationtransition, transparent to blue, occurs by electrochemical reduction.

While electrochromism was discovered in the 1960's, electrochromicdevices still unfortunately suffer various problems and have not begunto realize their full commercial potential. Electrochromic materials maybe incorporated into, for example, windows and mirrors. The color,transmittance, absorbance, and/or reflectance of such windows andmirrors may be changed by inducing a change in the electrochromicmaterial. However, advancements in electrochromic technology, apparatusand related methods of making and/or using them, are needed becauseconventional electrochromic windows suffer from, for example, highdefectivity and low versatility.

SUMMARY OF INVENTION

Herein are described window units, for example insulating glass units(IGU's), that have at least two panes, each pane having anelectrochromic (EC) device thereon. For example, when a window unit hastwo panes, each with two optical states, then the window unit may haveup to four optical states. Window units described herein allow thewindow user a greater choice, that is versatility, in how much light istransmitted through the electrochromic window, that is, the multi-paneIGU allows a gradation of transmission rather than a simple “on or off”conventional two-state window. Improved two-state windows are, however,an embodiment of the invention. Windows described herein allow the user,for example, to tailor the irradiation and heat load entering a room. Asecondary benefit is the improvement in defectivity due to non-alignedoptical defects. The inventors have discovered that by using two or morewindow panes, each with its own electrochromic device, registered in awindow unit, that is, one in front of the other, visual defects in anyof the individual devices are negated by virtue of the extremely smalllikelihood that any of the visual defects will align perfectly and thusbe observable to the user.

Virtually any electrochromic device or devices can be used incombination on panes of a window unit, however, low-defectelectrochromic devices work particularly well due to the lowerlikelihood that any visual defects will align and thus be observable tothe end user. In one embodiment, two-state, for example having a highand a low transmittance, all solid state low-defectivity electrochromicdevices, one on each of two opposing panes of a dual pane IGU are usedin order to create a four-state electrochromic window. In this way, theend user has four choices for how much light passes through the windowunit and there are virtually no detectable visual defects to theobserver when the electrochromic window is colored. Other advantages ofthis technology are described herein.

One embodiment is a window unit including: a first substantiallytransparent substrate and a first electrochromic device disposedthereon; a second substantially transparent substrate and a secondelectrochromic device disposed thereon; and a sealing separator betweenthe first and second substantially transparent substrates, which sealingseparator defines, together with the first and second substantiallytransparent substrates, an interior region that is thermally insulating.Embodiments include substrates of architectural glass scale and mayemploy a low emissivity coating. In certain embodiments, at least one ofthe first and second electrochromic devices faces the interior region,in some cases both the first and second electrochromic devices face theinterior region.

In one embodiment, at least one of the first and second electrochromicdevices is a two-state electrochromic device, in some embodiments bothof the first and second electrochromic devices are two-stateelectrochromic devices and the window unit has four optical states. Inone embodiment, when mounted, the first substantially transparentsubstrate of the window unit will face outside a room or building andthe second substantially transparent substrate will face inside saidroom or building. In one embodiment, each of the first and secondelectrochromic devices has its own high transmissive state and lowtransmissive state, and in a particular embodiment, the transmittance ofthe second electrochromic device's low transmissive state is higher thanthe transmittance of the first electrochromic device's low transmissivestate. In one embodiment, the transmittance of the first electrochromicdevice's low transmissive state is between about 5% and about 15%, andthe first electrochromic devices' high transmissive state is betweenabout 75% and about 95%; and the transmittance of the secondelectrochromic device's low transmissive state is between about 20% andabout 30%, and the second electrochromic devices' high transmissivestate is between about 75% and about 95%. For the purposes of thisembodiment, the device's transmissive states include the transmissivityof the substrate on which the substrate is constructed.

Window units described herein can have four optical states by virtue ofeach device having two optical states, colored or bleached,corresponding to a low transmissivity and a high transmissivity,respectively. Each of the four optical states is a product of thetransmissivity of the two electrochromic devices. In one embodiment, thewindow unit's four optical states are: i) overall transmittance ofbetween about 60% and about 90%; ii) overall transmittance of betweenabout 15% and about 30%; iii) overall transmittance of between about 5%and about 10%; and iv) overall transmittance of between about 0.1% andabout 5%.

In one embodiment, the electrochromic device on the substrate that willface the outside environment can be configured to better withstandenvironmental degradation than the electrochromic device on thesubstrate that faces the interior of a structure in which the windowunit is installed. In one embodiment, at least one of the first andsecond electrochromic devices is an entirely solid state and inorganicdevice.

Another embodiment is a method of fabricating a window unit, the methodincluding: arranging, substantially parallel to each other, a firstsubstantially transparent substrate with a first electrochromic devicedisposed thereon and a second substantially transparent substrate with asecond electrochromic device disposed thereon; and installing a sealingseparator between the first and second substantially transparentsubstrates, which sealing separator defines, together with the first andsecond substantially transparent substrates, an interior region, saidinterior region thermally insulating.

These and other features and advantages will be described in furtherdetail below, with reference to the associated drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

The following detailed description can be more fully understood whenconsidered in conjunction with the drawings in which:

FIG. 1 depicts a perspective exploded view of a multi-pane windowassembly.

FIG. 2 depicts a cross-section of a multi-pane window assembly.

FIG. 3 is a graph of the solar spectrum and representative curves for afour-state multi-pane window assembly.

FIG. 4 is a schematic cross-section of a multi-pane window assembly.

FIG. 5 is a schematic cross-section of an electrochromic device.

FIG. 6A is a schematic cross-section of an electrochromic device in ableached state.

FIG. 6B is a schematic cross-section of an electrochromic device in acolored state.

FIG. 7 is a schematic cross-section of an electrochromic device havingan ion conducting electronically insulating interfacial region ratherthan a distinct IC layer.

FIG. 8 is a schematic cross-section of an electrochromic device with aparticle in the ion conducting layer causing a localized defect in thedevice.

FIG. 9A is a schematic cross-section of an electrochromic device with aparticle on the conductive layer prior to depositing the remainder ofthe electrochromic stack.

FIG. 9B is a schematic cross-section of the electrochromic device ofFIG. 6A, where a “pop off” defect is formed during electrochromic stackformation.

FIG. 9C is a schematic cross-section of the electrochromic device ofFIG. 6B, showing an electrical short that is formed from the pop offdefect once the second conductive is deposited.

FIG. 10 depicts an integrated deposition system for makingall-solid-state electrochromic devices on architectural glass scalesubstrates.

DETAILED DESCRIPTION

Herein are described window units, for example IGU's, that have at leasttwo panes, each pane having an electrochromic device thereon. Forexample, when a window unit has two panes, each with two optical states,then the window unit can have four optical states. Window unitsdescribed herein allow the window user a greater choice of how muchlight is transmitted through the electrochromic window, that is, themulti-pane IGU concept allows a gradation of transmission rather than asimple “on or off” conventional two-state window. A secondary benefit isthe improvement in defectivity due to non-aligned optical defects, evenfor two-state windows. The inventors have discovered that by using twoor more window panes, each with its own electrochromic device,registered in a window unit, that is, one in front of the other, visualdefects in any of the individual devices are negated by virtue of theextremely small likelihood that any of the visual defects will alignperfectly and thus be observable to the user. Further benefits includeallowing usage of lower yield electrochromic glass, because defectivitycan be higher if two electrochromic panes are combined as described.This saves money both from a manufacturing standpoint as well asreducing waste streams. Additional benefits include enhanced depth ofcolor suitable for privacy glass applications, curtaining effects can beoffset in order to provide a more uniform coloration of the window, andindividual devices can be of unique color so as to provide some level ofcolor control.

Certain embodiments are described in relation to low-defectivity allsolid state and inorganic electrochromic devices, however, the inventionis not limited in this way. Virtually any electrochromic device ordevices can be used in combination, however, low-defect electrochromicdevices work particularly well due to the lower likelihood that anyvisual defects will align and thus be observable to the end user.

One of ordinary skill in the art would appreciate that “two-state”electrochromic devices refers to the bleached state and the coloredstate, each of which require an applied current. In reality, a two-stateEC device will actually have three states: bleached, colored andneutral. “Neutral” describes the ‘natural’ state of the window with nocharge applied, to either bleach or color the window (for example, FIG.5 shows an EC device in a neutral state, while FIGS. 6A and 6B showbleached and colored states, respectively). For the purposes of thisapplication, “states” of an electrochromic device are assumed to becolored or transparent states achieved by application of current to theEC device, although neutral states are inherent to the devices. Forexample, a “two-state” multi-pane electrochromic window, for examplehaving two panes, each with an electrochromic device, as describedherein, will actually have (net) states where one or both of theelectrochromic devices has no applied current. Thus if oneelectrochromic device is in a colored state and the other electrochromicdevice is “neutral” then collectively this constitutes an additionaloptical state for the window unit.

Multi-Pane Electrochromic Windows

In this application, a “window unit” includes two substantiallytransparent substrates, for example, two panes of glass, where eachsubstrate has at least one electrochromic device disposed thereon, andthe panes have a separator disposed between them. Since an IGU mayinclude more than two glass panes assembled into a unit, and forelectrochromic windows specifically may include electrical leads forconnecting the electrochromic glass to a voltage source, switches andthe like, the term “window unit” is used to convey a more simplesub-assembly. That is, for the purposes of this invention, an IGU mayinclude more components than a window unit. The most basic assembly of awindow unit is two substrates, each with an electrochromic devicethereon, and a sealing separator in between and registered with the twosubstrates.

The inventors have discovered that by using two or more electrochromicpanes in a window unit, visual defects in any of the individual devicesare negated by virtue of the extremely small likelihood that any of thevisual defects will align perfectly and thus be observable to the user.Virtually any electrochromic device or devices can be used incombination, however, low-defect electrochromic devices as describedabove work particularly well. In one embodiment, all solid statelow-defectivity electrochromic devices, one on each of two panes of anelectrochromic window, are employed opposing each other in an IGU. Inthis way, there are virtually no detectable visual defects to theobserver when, for example, both of the electrochromic panes arecolored.

One embodiment is a window unit including: a first substantiallytransparent substrate and a first electrochromic device disposedthereon; a second substantially transparent substrate and a secondelectrochromic device disposed thereon; and a sealing separator betweenthe first and second substantially transparent substrates, which sealingseparator defines, together with the first and second substantiallytransparent substrates, an interior region that is thermally insulating.

FIG. 1 depicts a window unit, 100, having a first substantiallytransparent substrate, 105, a separator, 110, and a second substantiallytransparent substrate, 115. Each of substrates 105 and 115 has anelectrochromic device (not shown) fabricated thereon. When the threecomponents are combined, where separator 110 is sandwiched in betweenand registered with substrates 105 and 115, window unit 100 is formed.Window unit 100 has an associated interior space defined by the faces ofthe substrates in contact with the separator and the interior surfacesof the separator. Separator 110 is typically a sealing separator, thatis, includes a spacer and sealing between the spacer and each substratewhere they adjoin in order to hermetically seal the interior region andthus protect the interior from moisture and the like. As a convention,for two-pane window units described herein, the four viewable surfacesof the substrates are indicated numerically. Surface 1 is the surface ofa substrate that is outside, for example, a room or building having sucha window unit in a window installed in a wall thereof. A stylized sun isincluded to indicate that surface 1 would be exposed to, for example,the outside environment. Surface 2 is the other surface of the substratethat is inside the interior space of the window unit. Surface 3 is thesurface of the second substrate that is inside the interior space of thewindow unit. Surface 4 is the other surface of the second substrate thatis outside the interior space of the window unit but inside, forexample, the aforementioned room or building. This convention does notnegate using window units described herein for entirely interior spacesin buildings, however, there are particular advantages to using them onexterior walls of buildings because of their optic as well as thermallyinsulating properties.

“Substantially transparent substrates” include those described herein inrelation to solid state inorganic electrochromic devices. That is, theyare substantially rigid, for example glass or plexiglass. The substratesof a window unit need not be made of the same material, for example, onesubstrate may be plastic while the other is glass. In another example,one substrate may be thinner than the other substrate, for example, thesubstrate that would face the interior of a structure, that is notexposed to the environment, may be thinner than the substrate that wouldface the exterior of the structure. In one embodiment, theelectrochromic device proximate the exterior environment, for example ofa building, is better able to withstand environmental degradation thanthe second electrochromic device, which is proximate the interior of thebuilding. In one embodiment, at least one of the first and secondsubstantially transparent substrates includes architectural glass. Inanother embodiment, at least one of the first and second substantiallytransparent substrates further includes a low emissivity coating. Inanother embodiment, at least one of the first and second substantiallytransparent substrates further includes a UV and/or infrared (IR)absorber, and/or, a UV and/or IR reflective layer. In one embodiment,the UV and/or IR reflective and/or absorber layer is on surface 1, inanother embodiment on surface 2, in yet another embodiment on surface 3,and in another embodiment on surface 4. In these embodiments, “on” asurface means on or associated with, considering that such layers orcoatings may be either in direct contact with the surface of the paneand/or on top of, for example, the EC stack that is on the surface ofthe substrate. One embodiment is any window unit described herein whereone or more of the EC devices has an UV and/or IR absorber and/or a UVand/or IR reflective layer thereon.

In one embodiment, at least one of the transparent conductive oxides ofone of the electrochromic devices is configured so that it can be heatedvia application of electricity independently of operation of theelectrochromic device to which it is a part. This is useful for a numberof reasons, for example, preheating the EC device prior to transitioningand/or to create an insulating barrier to ameliorate heat loss from theinterior of a building. Thus one embodiment is a window unit asdescribed herein, where one of the transparent conductive oxides of oneof the electrochromic devices is configured so that it can be heated viaapplication of electricity independently of operation of theelectrochromic device to which it is a part. One embodiment is atwo-pane electrochromic window as described herein, where each pane hasan EC device on its face in the interior region (surfaces 2 and 3) and atransparent conductive oxide of the EC device on surface 3 is configuredfor heating via application of electricity, said heating independentlyof operation of the EC device. Another embodiment is a two paneelectrochromic window unit as described in relation to FIG. 1, whereeach of the two electrochromic devices has a TCO that is configured forheating, independent of operation of the device to which it is acomponent. This configuration is particularly useful in cold climates,where the outside pane is colder, the TCO can be heated, for example,prior to transitioning the device to which it is a part, so that thedevice's transition is aided by prewarming. The TCO of the device on theinner pane can also be heated, for example, to create a thermallyinsulating barrier which keeps heat in a building.

The electrochromic devices on each of the transparent substrates neednot be of the same type. That is, one can be, for example, all inorganicand solid state while the other includes organic based electrochromicmaterials. In one embodiment, both electrochromic devices are all solidstate and inorganic, and in another embodiment both electrochromicdevices are also low-defectivity devices, for example low-defectivityall solid state and inorganic electrochromic devices as describedherein. By registering two such electrochromic devices as described,window units are produced that are virtually free of visible defectswhen colored.

The electrochromic devices need not necessarily face each other in theinterior region of the window unit (for example, on surfaces 2 and 3),but in one embodiment they do. This configuration is desirable becauseboth electrochromic devices are protected from the outside environmentin a sealed interior region of the window unit. It is also desirable forthe electrochromic devices to extend over substantially the entireviewable region of the transparent substrate on which they reside.

FIG. 2 depicts a cross-section of a window unit, 200, which includes anarchitectural glass pane, 205, with an electrochromic device, 210,disposed thereon. Window unit 200 also includes a second architecturalglass pane, 215, with an electrochromic device, 220, disposed thereon.Devices 210 and 220 face each other in the interior region of windowunit 200. A sealing separator, 225, seals the window unit, and in thisexample, overlaps the electrochromic devices. Electrical connections(not shown) might also pass through, or otherwise contact, separator225. Separator 225 may have a unitary body or be made of multiple parts,for example, a rigid or semi-rigid spacer and one or more adhesivesand/or sealing elements. In one example, separator 225 includes aspacer, such as a metal spacer, two seals that seal the areas where thespacer touches each of the panes, sometimes referred to as primaryseals, and a seal around the outer perimeter of the spacer, and betweenthe panes, sometimes called a secondary seal (for example a sealingadhesive). Separator 225 is simplified for the purposes of thedescription of FIG. 2.

As mentioned, due to the higher temperatures (due to absorption ofradiant energy by an electrochromic device on the glass) thatelectrochromic window units may experience, more robust separators andsealants than those used in conventional IGU's may be necessary. Sealingseparator 225 is disposed about peripheral regions of the first andsecond substantially transparent substrates without substantiallyobscuring a viewable region of the window unit (also, for example, asdepicted in FIG. 1). In one embodiment, the sealing separatorhermetically seals the interior region. The interior region of windowunit 200 is typically, but not necessarily, charged with an inert gassuch as argon or nitrogen. In one embodiment, the interior space issubstantially liquid free. In one embodiment the interior space ischarged with an inert gas and substantially liquid free. In oneembodiment, the interior space is substantially moisture free, that is,having a moisture content of less than about <0.1 ppm. In anotherembodiment, the interior space would require at least about −40° C. toreach dew point (condensation of water vapor from the interior space),in another embodiment at least about −70° C.

Pane 205 of window unit 200 is depicted as facing the exteriorenvironment (for example as illustrated by the sun's rays) while pane215 is facing the interior of a structure, for example an officebuilding, as illustrated by the outline figure of a man at work. Incertain embodiments, it is desirable to fabricate window units where theinner and outer electrochromic devices, that is, the device proximate tothe inside environment and the device proximate the outside environment,have different electrochromic states as far as transmissivity isconcerned. In one embodiment, at least one of the first and secondelectrochromic devices is a two-state electrochromic device. In anotherembodiment, both of the first and second electrochromic devices aretwo-state electrochromic devices and, thus the window unit has fouroptical states. In one embodiment, such a window unit, when mounted,will have the first substantially transparent substrate facing outside aroom or building and the second substantially transparent substrate willface inside the room or building, and where each of the first and secondelectrochromic devices has its own high transmissive state and lowtransmissive state, and where the transmittance of the secondelectrochromic device's low transmissive state is higher than thetransmittance of the first electrochromic device's low transmissivestate. In this context, the “device's” transmissive state means eitherthe device itself or the combination of the transmissivity of the deviceand the substrate upon which it is deposited. That is, for example, mostsubstrates have some inherent absorptive properties, for example, floatglass alone typically has a transmissivity of about 92%.

One reason that it is desirable to have the first (exterior) device'slow transmissive state is lower than the second (interior) device's lowtransmissive state, is that the device proximate the exterior can blockmore light (and therefore heat) transmission and thus ease therequirements of the interior device. For example, since the outer devicefilters out a good portion of the solar spectrum, the inner device isprotected from degradation as compared to a device without suchprotection. So, the EC device on the inner pane, for example, need notbe as robust, for example, all solid state and inorganic.

Another advantage to a multi-pane, for example a two-pane window with adevice on each pane, is that neither device need have stringent lowertransmissivity, for example less than 10% transmissivity, because thenet transmissivity through the window unit is a product of both device'stransmissivity. Yet another advantage is that each device can be thinnerthan either would otherwise be if the window unit had, and relied on,only a single electrochromic device. Thinner devices translates intoless materials used which saves in manufacturing costs. Thinner devicesalso translate into faster response times during transition, which savesmoney, for example, by using less electricity and controlling heat loadentering a room more quickly, and makes a more attractive window for theend user.

Another advantage of windows with more than one electrochromic pane, forexample two electrochromic panes as described in relation to FIG. 2, isthat electrical charge for powering the panes can be shared between thepanes by a controller, for example, an appropriately programmedcomputer, which includes program instructions for carrying out chargesharing operations between the two electrochromic panes. Thus, oneembodiment is a method of operating a multi-pane electrochromic window,including sharing electrical charge between panes of the multi-paneelectrochromic window.

Still yet another advantage of a multi-pane electrochromic window unitrelates to the curtaining effect. When electrochromic windows transitionfrom dark to light, or light to dark, there is typically a transitionperiod, that is, the transition is not instantaneous. During thetransition, there can be visual anomalies and/or the transition is notuniform across the viewable surface of the window. For example, in awindow where the bus bars that supply voltage to an electrochromicdevice, the bus bars may be arranged on opposite sides, for example, topand bottom, of the device in the IGU. When such a window transitions,for example, from light to dark, the device darkens as a function of thesheet resistance variation over the surface of the device. Thus theedges darken first, and there is a front, even or not, of darkening thatemanates from each bus bar and travels toward the center of the window.The two fronts meet somewhere in the viewable region and eventually thewindow completes the transition to the dark state. This can detract fromthe appearance of the window during transitions. However, for example,with a dual pane electrochromic window with an electrochromic device oneach pane, the transitions can be made to complement each other andminimize the curtaining effect. For example, if one pane's bus bars areon the top and bottom of the pane, and the other pane's bus bars are oneither side of that pane, that is orthogonal to the first pane'sbusbars, then the transitions, for example when both devices aredarkening, will complement each other so that more area darkens faster.In another example, a first pane's busbars are arranged so that thefirst panel darkens/lightens from the center out, while a second pane'sbusbars are arranged so the second panel darkens/lightens from perimeterinward. In this way the curtaining effect of each pane compliments theother, thereby minimizing the overall curtaining effect as viewed by theuser.

In one embodiment, the two or more electrochromic devices of amulti-pane electrochromic window, each having two optical states, arecoupled (active or not, concurrently) so that they are all on or alloff. In this way, when on, no, or substantially no, visual defects arediscernable to the naked eye. That is, their high and low transmissivitystates are employed together, both high or both low. This is a two-statemulti-pane electrochromic window. As noted, there is of course a neutralstate, where there is no applied current, associated with each two-statedevice, and states where one or both panes have no applied current aremeant to be included in the two-state window.

Another embodiment is a four-state multi-pane electrochromic window. Inone embodiment, the four-state window has two panes, each with two-stateelectrochromic device. By virtue of each pane having a high and a lowtransmissivity state, when combined, there are four possible states forthe electrochromic window which includes the electrochromic panes. Anexample of such a two-pane window unit device transmissivityconfiguration is illustrated in Table 1. In this example, each of theinner and outer window panes has two-states, on and off, eachcorresponding to a low and a high transmissivity state, respectively.For example, an inner pane has a high transmissivity of 80% and a lowtransmissivity of 20%, while an outer pane has a high transmissivity of80% and a low transmissivity of 10%. Since each window pane's device hastwo optical states, that is a highly transmissive state and a lowtransmissive state, and they are combined in all possible ways, thewindow unit has four optical states.

As outlined in Table 1, for example, state 1 exists when the innerpane's electrochromic device is off and the outer pane's electrochromicdevice is off. Since both devices have an 80% transmissivity, when bothelectrochromic devices are off the net transmissivity through both panesis 64% (that is, 80% of 80%). So, when the window as a whole is drawingno power, the panes collectively allow 64% of the ambient light passthrough the window unit. State 2 exists when the inner pane's device ison but the outer pane's device is off, thus allowing a nettransmissivity of 16% (20% of 80%). State 3 exists when the inner pane'sdevice is off but the outer pane's device is on, thus allowing a nettransmissivity of 8% (80% of 10%). State 4 exists when the inner pane'sdevice is on and the outer pane's device is on, thus allowing a nettransmissivity of 2% (20% of 10%). Thus, a four-state electrochromicwindow allows a user to choose from four optical states, from highlytransmissive, for example when one wants more light to enter a room, tovery low transmissivity, for example when one wants the room to be dark,for example during a slide presentation. In state 1, there are noobservable optical defects because neither of the electrochromic devicesis in the dark state. In state 4, there are no observable opticaldefects because the likelihood of alignment of two defects, each on oneof the devices, is extremely small, therefore one device's opacitynecessarily blocks the other pane's optical defect.

The user can also choose two intermediate states of transmissivity whichprovides more flexibility than a simple two-state, that is light ordark/off or on, electrochromic window. Optical defects are also lesslikely to be observable in these two intermediate transmissivity statesbecause, although one pane's device is off, the pane that is active isblocking, in this example, only 80% or 90% of the light transmissionsthat would otherwise pass through the window panes. The visibility ofoptical defects is proportional to the transmission and background ofthe window. Visible defects are most obvious when a very dark window isplaced in front of a very bright background, that is, 1% Tvis windowwith a pinhole against direct sun. Because the window is not as dark,for example as in state 4 where 98% of the light is blocked, any opticaldefects present are less noticeable because they are not contrasted ashighly as they would be when the electrochromic device is much darker.This is another advantage of configuring the device with the higher lowtransmissivity state as the inner pane, because there is less contrastbetween optical defects and the darkened portion of the device, forexample in state 2 when the inner pane blocks 80% of the light, vs.state 3 when 90% of the light is blocked by the outer pane. During state3, when 90% of the light is blocked by the outer pane, there is anadditional inner pane through which any contrast would have to beobserved by the user. The inner pane may impart some reflectivity and orrefractive properties that would make observing optical defects in theouter pane in state 3 less likely. Nevertheless, low-defectivity windowsalso decrease the observable optical defects.

TABLE 1 Inner Pane Outer Pane 80% high (off) 80% high (off) Net State20% low (on) 10% low (on) Transmissivity 1 off off 64% 2 on off 16% 3off on 8% 4 on on 2%

FIG. 3 is a graphical representation that approximates the solarspectrum (solid line). As can be seen, a significant amount of nearinfrared radiation passes through a standard window and thus unwantedheating of interiors of buildings having such windows occurs. Alsodepicted in FIG. 3 are transmissivity curves for the four optical statesas described in relation to Table 1, each curve (dotted lines) labeled1, 2, 3 and 4, respectively. For example, curve 1 has a maximum at about550 nm in the visible range, which corresponds to the net transmissivityof 64% (state 1), that is, the light level the user would actuallyobserve through the window unit. State 1 allows a substantial amount oflight to pass through the window unit, and also a significant portion ofthe near infrared spectrum, which allows passive solar heating ifdesired. This is in contrast to a typical low-E coating which, althoughallows a comparable amount of visible light to pass through, blocks mostof the near infrared spectrum and does not allow passive solar heatingin the winter (although embodiments described herein include low-Ecoatings). States 2-4 allow much less light in, but also much less ofthe near infrared spectrum, and thus unwanted interior heating isdrastically reduced, for example, allowing savings on energy used tocool a building during hot summer months. Thus it is desirable to havemore than two-states for electrochromic windows, the intermediate statesallow for tailored light and/or heat control as desired. Electrochromicwindow units as described herein also reduce a significant amount of theultraviolet spectrum from entering the interior of a building.

Thus one embodiment is a window unit where the transmittance of thefirst (outer) electrochromic device's low transmissive state is betweenabout 5% and about 15%, and the first electrochromic devices' hightransmissive state is between about 75% and about 95%; and thetransmittance of the second (inner) electrochromic device's lowtransmissive state is between about 20% and about 30%, and the secondelectrochromic devices' high transmissive state is between about 75% andabout 95%. In one embodiment, as a product of two device's high and lowtransmissivity values, a window unit has four optical states of: i)overall (net) transmittance of between about 60% and about 90%; ii)overall transmittance of between about 15% and about 30%; iii) overalltransmittance of between about 5% and about 10%; and iv) overalltransmittance of between about 0.1% and about 5%.

In one embodiment, both of the first and second substantiallytransparent substrates are architectural glass. By using twolow-defectivity electrochromic devices, even on architectural scaleglass substrates, registered for example as in FIGS. 1 and 2, the windowunit has virtually no visible defects. One embodiment is an IGUconstructed from a window unit described herein. Architectural glasswindow units are particularly desirable due to the large demand forcontrolling energy costs in large buildings.

One embodiment is an IGU including: a first pane of architectural glassincluding a first electrochromic device disposed thereon; a second paneof architectural glass including a second electrochromic device disposedthereon; a sealing separator between the first and second panes, whichsealing separator defines, together with the first and second panes, aninterior region between the first and second panes; and an inert gas orvacuum in the interior region; where both the first electrochromicdevice and the second electrochromic device are in the interior region.One or both of the panes in the IGU can have a Low-E coating. In oneembodiment, both the first electrochromic device and the secondelectrochromic device are entirely solid state and inorganic. In anotherembodiment, both of the first and second electrochromic devices aretwo-state electrochromic devices and the IGU has four optical states. Inone embodiment, the four optical states are: i) overall transmittance ofbetween about 60% and about 90%; ii) overall transmittance of betweenabout 15% and about 30%; iii) overall transmittance of between about 5%and about 10%; and iv) overall transmittance of between about 0.1% andabout 5%. In one embodiment, the IGU has no visible defects.

In accord with the device embodiments described are complementarymethods. One embodiment is a method of providing a gradation oftransmissivity in an electrochromic window, including: (i) combining afirst electrochromic window pane and a second electrochromic window paneinto an IGU, wherein each of the first and second electrochromic paneshas two optical states, a high transmissivity and a low transmissivity;and (ii) operating the two electrochromic window panes in four modes,including: 1. both panes at their high transmissivity; 2. the firstelectrochromic window pane at its low transmissivity and the secondelectrochromic window pane at its high transmissivity; 3. the firstelectrochromic window pane at its high transmissivity and the secondelectrochromic window pane at its low transmissivity; and 4. both panesat their low transmissivity. In one embodiment, the first electrochromicwindow pane is the inner pane of the electrochromic window and thesecond electrochromic window pane is the outer pane of theelectrochromic window, and the first electrochromic pane's lowtransmissivity is greater than the second electrochromic window pane'slow transmissivity.

One embodiment is a multi-pane electrochromic window where each paneincludes an electrochromic device and where at least one of theelectrochromic devices has intermediate state capability, that is, canachieve variable coloring states between the extreme end states, thatis, fully darkened and fully lightened states. The value of thisembodiment is a wider dynamic range of states, rather than “digital”states as described, for example, with respect to Table 1. In oneembodiment, the window unit has two panes of glass, in anotherembodiment, three panes of glass.

Another aspect of the invention is a multipane EC window unit having oneor more EC devices, each on a separate pane of the window unit, thewindow unit including a pane that does not have an EC device, but thatdoes include at least a heatable transparent conductive oxide. In oneembodiment, the “TCO-only” pane of the window unit can also include UVand/or IR absorbing and/or reflecting coatings, lowE coatings and thelike. As described herein, the transparent conductive oxide can beheated via, for example, busbars which supply electricity to run acurrent through the transparent conductive oxide. In one embodiment, thewindow unit has three panes, two each with their own EC device, and athird pane with the heatable transparent conductive oxide. In oneembodiment, the order of the panes is a first pane with an EC device, asecond pane with an EC device, and then the third pane with the heatableTCO. In one embodiment, the first and second panes, each with an ECdevice, can be configured so that the EC devices are, with reference tothe surfaces in FIG. 1, for example, on surfaces 2 and 3, or, forexample, on surfaces 2 and 4; in combination with the TCO on the thirdpane facing, for example, surface 4. That is, second EC pane and the TCOonly pane, along with a separator as described herein, for a secondinterior region where the EC device of the second pane and the TCO ofthe TCO-only pane are in the second interior region. In one example, thethird pane is the inner most pane in the interior of a building when thewindow unit is installed. In another example the third pane is inbetween the first and second panes, each of which have an EC devicethereon.

FIG. 4 illustrates two configurations of a three-pane window unit havingtwo EC panes, each with an EC device, and a third pane with a heatableTCO. Configuration 400 a shows a first pane (as described herein) 405,with an EC device (as described herein), 410. A separator (as describedherein), 425 a, separates and seals a first inner region between pane405 and pane 415. Pane 415 has an EC device, 420, thereon. A secondseparator, 425 b, separates and seals a second inner region, betweenpane 415 and a third pane, 435, which has a heatable TCO, 430, thereon.In configuration 400 b, EC device 420 is in the second interior space,opposite and facing TCO 430. One of ordinary skill in the art wouldappreciate that the EC devices or the TCO can be on faces of the panesthat are exposed to ambient conditions, rather than an interior region,without escaping the scope of the invention.

Another embodiment is window unit as described in relation to FIG. 4,but where each of 410, 420 and 430 are each electrochromic devices asdescribed herein. In one embodiment, devices 410 and 430 are all solidstate and inorganic, and device 420 is an organic based EC device,either on a glass substrate or a polymeric film. In another embodimentall three EC devices are all solid state and inorganic.

Another embodiment is a window unit as described in relation to FIG. 4,but where 420 and 415 are replaced with a UV and/or IR absorber and/orreflective film and the outer two panes are EC device panes as describedherein. For example, one embodiment is a window unit with two EC panesand one or more UV and/or IR absorber and/or reflective films disposedin the interior space. The configuration in FIG. 4 (with two spacers) isone way to implement this embodiment.

One embodiment is a window unit as described herein where a transparentconductive oxide of at least one of the EC devices is heatable, forexample, via application of electricity to resistively heat the TCO. Oneembodiment is a two-pane electrochromic window as described herein,where each pane has an EC device on its face in the interior region(surfaces 2 and 3 as described in relation to FIG. 1) and at least onetransparent conductive oxide of one of the EC devices is configured forheating via application of electricity, said heating independently ofoperation of the EC device. When installed in a building where one paneis exposed to the outside and the other exposed to the inside, thisheatable TCO can be on the side facing the interior or the exterior ofthe building. As described above, when two heatable TCO's are used thereare associated insulative and EC transition benefits.

Another aspect is a multipane EC window unit, having two panes(substrates) where the first substrate has an electrochromic device, thesecond transparent substrate does not, but the second substrate doesinclude a transparent conductive oxide, for example indium tin oxide,that can be heated, for example via application of electricity appliedvia busbars. In one example, the window unit is configured analogouslyto that depicted in FIG. 2, but where, for example, 220 is not an ECdevice, but rather a heatable TCO. Thus one embodiment is a window unitincluding: a first substantially transparent substrate and anelectrochromic device disposed thereon; a second substantiallytransparent substrate and a heatable transparent conductive oxide layerthereon; and a sealing separator between the first and secondsubstantially transparent substrates, which sealing separator defines,together with the first and second substantially transparent substrates,an interior region that is thermally insulating. In one embodiment, theelectrochromic device and the heatable transparent conductive oxide areboth in the interior region. In one embodiment, the second substantiallytransparent substrate comprises an infrared reflective and/or infraredabsorbing coating. In one embodiment, the electrochromic device is allsolid state and inorganic.

The advantages to the above configurations include: 1) improvedinsulating properties (U value), 2) more flexibility in the materialsused for the suspended film (i.e. organic based) as some UV/IR filteringwould occur through, for example, a first, more robust inorganic device,which would allow use of less robust organic devices in the interiorregion of the window unit, and 3) utilizing an transparent conductingoxide as a heating element for insulating and/or aiding in ECtransitions, for example, at low temperature conditions, to stem heatloss through the window, for example, during the night and/or coolerweather.

Another embodiment is a method of changing between multiple opticalstates in a window unit, including: (i) changing the optical state of afirst electrochromic device of a first substantially transparentsubstrate without changing the optical state of a second electrochromicdevice on a second substantially transparent substrate, where the windowunit includes the first and second substantially transparent substratesconnected by a sealing separator that defines, together with the firstand second substantially transparent substrates, an interior region; and(ii) changing the optical state of the second electrochromic devicewithout changing the optical state of the first electrochromic device.This method can further include changing the optical state of the firstelectrochromic device concurrently with changing the optical state ofthe second electrochromic device. By combining these actions, a windowunit has multiple optical states for the end user.

Another embodiment is a method of fabricating a window unit, the methodincluding: arranging, substantially parallel to each other, a firstsubstantially transparent substrate with a first electrochromic devicedisposed thereon and a second substantially transparent substrate with asecond electrochromic device disposed thereon; and installing a sealingseparator between the first and second substantially transparentsubstrates, which sealing separator defines, together with the first andsecond substantially transparent substrates, an interior region, theinterior region thermally insulating. In one embodiment, at least one ofthe first and second substantially transparent substrates includesarchitectural glass. In one embodiment, at least one of the first andsecond substantially transparent substrates further includes a lowemissivity coating. In another embodiment, both the first and secondelectrochromic devices face the interior region. In one embodiment, atleast one of the first and second electrochromic devices is a two-stateelectrochromic device, in another embodiment, both of the first andsecond electrochromic devices are two-state electrochromic devices andthe window unit has four optical states. In one embodiment, at least oneof the first and second electrochromic devices is an entirely solidstate and inorganic device. In one embodiment, the transmittance of thefirst electrochromic device's low transmissive state is between about 5%and about 15%, and the first electrochromic devices' high transmissivestate is between about 75% and about 95%; and the transmittance of thesecond electrochromic device's low transmissive state is between about20% and about 30%, and the second electrochromic devices' hightransmissive state is between about 75% and about 95%. In oneembodiment, the four optical states are: i) overall transmittance ofbetween about 60% and about 90%; ii) overall transmittance of betweenabout 15% and about 30%; iii) overall transmittance of between about 5%and about 10%; and iv) overall transmittance of between about 0.1% andabout 5%. The sealing separator hermetically seals the interior regionand the interior region can contain an inert gas or vacuum and/or besubstantially liquid free. In one embodiment, the window unit has novisible defects. In another embodiment, the window unit is an IGU.

Another embodiment is a method of fabricating an IGU, the methodincluding: arranging a first pane of architectural glass and a secondpane of architectural glass in a substantially parallel arrangement,where the first pane includes a first electrochromic device disposedthereon, and the second pane includes a second electrochromic devicedisposed thereon; installing a sealing separator between the first andsecond panes, which sealing separator defines, together with the firstand second panes, an interior region between the first and second panes,the interior region thermally insulating; and charging the interiorregion with an inert gas; where the first electrochromic device and thesecond electrochromic device are in the interior region and are bothentirely solid state and inorganic. In one embodiment, at least one ofthe first and second panes further includes a low emissivity coating. Inanother embodiment, both of the first and second electrochromic devicesare two-state electrochromic devices and the IGU has four opticalstates. In one embodiment, the four optical states are: i) overalltransmittance of between about 60% and about 90%; ii) overalltransmittance of between about 15% and about 30%; iii) overalltransmittance of between about 5% and about 10%; and iv) overalltransmittance of between about 0.1% and about 5%. In one embodiment, theIGU has no visible defects.

As described, virtually any electrochromic device will work with thisinvention. In some embodiments, more than one type of electrochromicdevice is used in a window unit, for example, a more robustelectrochromic device is used on an outer pane while a less robustdevice is used on an inner pane. Particularly well suited for thisinvention are all solid state and inorganic electrochromic devices.Thus, for context and in relation to embodiments that include suchdevices, electrochromic device technology is described below in relationto two types of all solid state and inorganic electrochromic devices,particularly low-defectivity all solid state and inorganicelectrochromic devices. Because of their low defectivity and robustnature, these devices are particularly well suited for embodimentsdescribed herein. One embodiment of the invention is any describedembodiment including one or more electrochromic devices, where the oneor more electrochromic devices are selected from the first and secondtypes described below. In a particular embodiment, the one or moreelectrochromic devices are low-defectivity devices, where thedefectivity level is defined below. The first type are devices havingdistinct material layers in the electrochromic stack, the second typeare devices having an ion conducting electronically insulatinginterfacial region which serves the function of a distinct ionconducting layer as in the first type.

Low-Defectivity Solid State and Inorganic Electrochromic Devices HavingDistinct Layers

FIG. 5 depicts a schematic cross-section of an electrochromic device,500. Electrochromic device 500 includes a substrate, 502, a conductivelayer (CL), 504, an electrochromic layer (EC), 506, an ion conductinglayer (IC), 508, a counter electrode layer (CE), 510, and a conductivelayer (CL), 514. Layers 504, 506, 508, 510, and 514 are collectivelyreferred to as an electrochromic stack, 520. A voltage source, 516,operable to apply an electric potential across electrochromic stack 520,effects the transition of the electrochromic device from, for example, ableached state to a colored state (depicted). The order of layers can bereversed with respect to the substrate.

Electrochromic devices having distinct layers as described can befabricated as all solid state and inorganic devices with lowdefectivity. Such all solid-state and inorganic electrochromic devices,and methods of fabricating them, are described in more detail in U.S.patent application Ser. No. 12/645,111, entitled, “Fabrication ofLow-Defectivity Electrochromic Devices,” filed on Dec. 22, 2009 andnaming Mark Kozlowski et al. as inventors, and in U.S. patentapplication Ser. No. 12/645,159, entitled, “Electrochromic Devices,”filed on Dec. 22, 2009 and naming Zhongchun Wang et al. as inventors,both of which are incorporated by reference herein for all purposes.

It should be understood that the reference to a transition between ableached state and colored state is non-limiting and suggests only oneexample, among many, of an electrochromic transition that may beimplemented. Unless otherwise specified herein, whenever reference ismade to a bleached-colored transition, the corresponding device orprocess encompasses other optical state transitions suchnon-reflective-reflective, transparent-opaque, etc. Further the term“bleached” refers to an optically neutral state, for example, uncolored,transparent or translucent. Still further, unless specified otherwiseherein, the “color” of an electrochromic transition is not limited toany particular wavelength or range of wavelengths. As understood bythose of skill in the art, the choice of appropriate electrochromic andcounter electrode materials governs the relevant optical transition.

In certain embodiments, the electrochromic device reversibly cyclesbetween a bleached state and a colored state. In the bleached state, apotential is applied to the electrochromic stack 520 such that availableions in the stack that can cause the electrochromic material 506 to bein the colored state reside primarily in the counter electrode 510. Whenthe potential on the electrochromic stack is reversed, the ions aretransported across the ion conducting layer 508 to the electrochromicmaterial 506 and cause the material to enter the colored state. A moredetailed description of the transition from bleached to colored state,and from colored to bleached state, is described below.

In certain embodiments, all of the materials making up electrochromicstack 520 are inorganic, solid (that is, in the solid state), or bothinorganic and solid. Because organic materials tend to degrade overtime, inorganic materials offer the advantage of a reliableelectrochromic stack that can function for extended periods of time.Materials in the solid state also offer the advantage of not havingcontainment and leakage issues, as materials in the liquid state oftendo. Each of the layers in the electrochromic device is discussed indetail, below. It should be understood that any one or more of thelayers in the stack may contain some amount of organic material, but inmany implementations one or more of the layers contains little or noorganic matter. The same can be said for liquids that may be present inone or more layers in small amounts. It should also be understood thatsolid state material may be deposited or otherwise formed by processesemploying liquid components such as certain processes employing sol-gelsor chemical vapor deposition.

Referring again to FIG. 5, voltage source 516 is typically a low voltageelectrical source and may be configured to operate in conjunction withradiant and other environmental sensors. Voltage source 516 may also beconfigured to interface with an energy management system, such as acomputer system that controls the electrochromic device according tofactors such as the time of year, time of day, and measuredenvironmental conditions. Such an energy management system, inconjunction with large area electrochromic devices (that is, anelectrochromic window), can dramatically lower the energy consumption ofa building. As will be apparent from the description of multi-paneelectrochromic windows described herein, particular energy savings onheating and cooling are realized.

Any material having suitable optical, electrical, thermal, andmechanical properties may be used as substrate 502. Such substratesinclude, for example, glass, plastic, and mirror materials. Suitableplastic substrates include, for example acrylic, polystyrene,polycarbonate, allyl diglycol carbonate, SAN (styrene acrylonitrilecopolymer), poly(4-methyl-1-pentene), polyester, polyamide, etc. If aplastic substrate is used, it is preferably barrier protected andabrasion protected using a hard coat of, for example, a diamond-likeprotection coating, a silica/silicone anti-abrasion coating, or thelike, such as is well known in the plastic glazing art. Suitable glassesinclude either clear or tinted soda lime glass, including soda limefloat glass. The glass may be tempered or untempered. In someembodiments of electrochromic device 500 with glass, for example sodalime glass, used as substrate 502, there is a sodium diffusion barrierlayer (not shown) between substrate 502 and conductive layer 504 toprevent the diffusion of sodium ions from the glass into conductivelayer 504.

In some embodiments, the optical transmittance (that is, the ratio oftransmitted radiation or spectrum to incident radiation or spectrum) or“transmissivity” of substrate 502 is about 40 to 95%, for example, about90-92%. The substrate may be of any thickness, as long as it hassuitable mechanical properties to support the electrochromic stack 520.While substrate 502 may be of virtually any suitable thickness, in someembodiments, it is about 0.01 mm to 10 mm thick, preferably about 3 mmto 9 mm thick. Multi-pane window units described herein may haveindividual panes of different thickness. In one embodiment, an inner(proximate to the interior of a structure) pane is thinner than an outer(proximate to the external environment) pane that must withstand moreextreme exposure.

In some embodiments, the substrate is architectural glass. Architecturalglass is glass that is used as a building material. Architectural glassis typically used in commercial buildings, but may also be used inresidential buildings, and typically, though not necessarily, separatesan indoor environment from an outdoor environment. In certainembodiments, architectural glass is at least 20 inches by 20 inches, andcan be much larger, for example, as large as about 72 inches by 120inches. Architectural glass is typically at least about 2 mm thick.Architectural glass that is less than about 3.2 mm thick cannot betempered. In some embodiments with architectural glass as the substrate,the substrate may still be tempered even after the electrochromic stackhas been fabricated on the substrate. In some embodiments witharchitectural glass as the substrate, the substrate is a soda lime glassfrom a tin float line. The percent transmission over the visiblespectrum of an architectural glass substrate (that is, the integratedtransmission across the visible spectrum) is generally greater than 80%for neutral substrates, but it could be lower for colored substrates.Preferably, the percent transmission of the substrate over the visiblespectrum is at least about 90% (for example, about 90-92%). The visiblespectrum is the spectrum that a typical human eye will respond to,generally about 380 nm (purple) to about 780 nm (red). In some cases,the glass has a surface roughness of between about 10 and 30 nm.

On top of substrate 502 is conductive layer 504. In certain embodiments,one or both of the conductive layers 504 and 514 is inorganic and/orsolid. Conductive layers 504 and 514 may be made from a number ofdifferent materials, including conductive oxides, thin metalliccoatings, conductive metal nitrides, and composite conductors.Typically, conductive layers 504 and 514 are transparent at least in therange of wavelengths where electrochromism is exhibited by theelectrochromic layer. Transparent conductive oxides include metal oxidesand metal oxides doped with one or more metals. Examples of such metaloxides and doped metal oxides include indium oxide, indium tin oxide,doped indium oxide, tin oxide, doped tin oxide, zinc oxide, aluminumzinc oxide, doped zinc oxide, ruthenium oxide, doped ruthenium oxide andthe like. Since oxides are often used for these layers, they aresometimes referred to as “transparent conductive oxide” (TCO) layers.Thin metallic coatings that are substantially transparent may also beused. Examples of metals used for such thin metallic coatings includetransition metals including gold, platinum, silver, aluminum, nickelalloy, and the like. Thin metallic coatings based on silver, well knownin the glazing industry, are also used. Examples of conductive nitridesinclude titanium nitrides, tantalum nitrides, titanium oxynitrides, andtantalum oxynitrides. The conductive layers 504 and 514 may also becomposite conductors. Such composite conductors may be fabricated byplacing highly conductive ceramic and metal wires or conductive layerpatterns on one of the faces of the substrate and then over-coating withtransparent conductive materials such as doped tin oxides or indium tinoxide. Ideally, such wires should be thin enough as to be invisible tothe naked eye (for example, about 100 □m or thinner).

In some embodiments, commercially available substrates such as glasssubstrates contain a transparent conductive layer coating. Such productsmay be used for both substrate 502 and conductive layer 504. Examples ofsuch glasses include conductive layer coated glasses sold under thetrademark TEC Glass™ by Pilkington of Toledo, Ohio, and SUNGATE™ 300 andSUNGATE™ 500 by PPG Industries of Pittsburgh, Pa. TEC Glass™ is a glasscoated with a fluorinated tin oxide conductive layer. Indium tin oxideis also a commonly used substantially transparent conductive layer.

In some embodiments, the same conductive layer is used for bothconductive layers (that is, conductive layers 504 and 514). In someembodiments, different conductive materials are used for each conductivelayer 504 and 514. For example, in some embodiments, TEC Glass™ is usedfor substrate 502 (float glass) and conductive layer 504 (fluorinatedtin oxide) and indium tin oxide is used for conductive layer 514. Asnoted above, in some embodiments employing TEC Glass™ there is a sodiumdiffusion barrier between the glass substrate 502 and TEC conductivelayer 504 because float glass may have a high sodium content.

In some implementations, the composition of a conductive layer, asprovided for fabrication, should be chosen or tailored based on thecomposition of an adjacent layer (for example, electrochromic layer 506or counter electrode layer 510) in contact with the conductive layer.For metal oxide conductive layers, for example, conductivity is afunction of the number of oxygen vacancies in the conductive layermaterial, and the number of oxygen vacancies in the metal oxide isimpacted by the composition of the adjacent layer. Selection criteriafor a conductive layer may also include the material's electrochemicalstability and ability to avoid oxidation or more commonly reduction by amobile ion species.

The function of the conductive layers is to spread an electric potentialprovided by voltage source 516 over surfaces of the electrochromic stack520 to interior regions of the stack, with very little ohmic potentialdrop. The electric potential is transferred to the conductive layersthough electrical connections to the conductive layers. In someembodiments, bus bars, one in contact with conductive layer 504 and onein contact with conductive layer 514, provide the electric connectionbetween the voltage source 516 and the conductive layers 504 and 514.The conductive layers 504 and 514 may also be connected to the voltagesource 516 with other conventional means.

In some embodiments, the thickness of conductive layers 504 and 514 isbetween about 5 nm and about 10,000 nm. In some embodiments, thethickness of conductive layers 504 and 514 are between about 10 nm andabout 1,000 nm. In other embodiments, the thickness of conductive layers504 and 514 are between about 10 nm and about 500 nm. In someembodiments where TEC Glass™ is used for substrate 502 and conductivelayer 504, the conductive layer is about 400 nm thick. In someembodiments where indium tin oxide is used for conductive layer 514, theconductive layer is about 100 nm to 400 nm thick (280 nm in oneembodiment). More generally, thicker layers of the conductive materialmay be employed so long as they provide the necessary electricalproperties (for example, conductivity) and optical properties (forexample, transmittance). Generally, the conductive layers 504 and 514are as thin as possible to increase transparency and to reduce cost. Insome embodiment, conductive layers are substantially crystalline. Insome embodiment, conductive layers are crystalline with a high fractionof large equiaxed grains

The thickness of the each conductive layer 504 and 514 is alsosubstantially uniform. Smooth layers (that is, low roughness, Ra) of theconductive layer 504 are desirable so that other layers of theelectrochromic stack 520 are more compliant. In one embodiment, asubstantially uniform conductive layer varies by no more than about ±10%in each of the aforementioned thickness ranges. In another embodiment, asubstantially uniform conductive layer varies by no more than about ±5%in each of the aforementioned thickness ranges. In another embodiment, asubstantially uniform conductive layer varies by no more than about ±2%in each of the aforementioned thickness ranges.

The sheet resistance (R_(s)) of the conductive layers is also importantbecause of the relatively large area spanned by the layers. In someembodiments, the sheet resistance of conductive layers 504 and 514 isbetween about 5 Ohms per square to about 30 Ohms per square. In someembodiments, the sheet resistance of conductive layers 504 and 514 isabout 15 Ohms per square. In general, it is desirable that the sheetresistance of each of the two conductive layers be about the same. Inone embodiment, the two layers each have a sheet resistance of betweenabout 10 and about 15 Ohms per square.

Overlaying conductive layer 504 is electrochromic layer 506. Inembodiments, electrochromic layer 506 is inorganic and/or solid, intypical embodiments inorganic and solid. The electrochromic layer maycontain any one or more of a number of different electrochromicmaterials, including metal oxides. Such metal oxides include tungstenoxide (WO₃), molybdenum oxide (MoO₃), niobium oxide (Nb₂O₅), titaniumoxide (TiO₂), copper oxide (CuO), iridium oxide (Ir₂O₃), chromium oxide(Cr₂O₃), manganese oxide (Mn₂O₃), vanadium oxide (V₂O₅), nickel oxide(Ni₂O₃), cobalt oxide (Co₂O₃) and the like. In some embodiments, themetal oxide is doped with one or more dopants such as lithium, sodium,potassium, molybdenum, vanadium, titanium, and/or other suitable metalsor compounds containing metals. Mixed oxides (for example, W—Mo oxide,W—V oxide) are also used in certain embodiments. An electrochromic layer506 comprising a metal oxide is capable of receiving ions transferredfrom counter electrode layer 510.

In some embodiments, tungsten oxide or doped tungsten oxide is used forelectrochromic layer 506. In one embodiment, the electrochromic layer ismade substantially of WO_(x), where “x” refers to an atomic ratio ofoxygen to tungsten in the electrochromic layer, and x is between about2.7 and 3.5. It has been suggested that only sub-stoichiometric tungstenoxide exhibits electrochromism; that is, stoichiometric tungsten oxide,WO₃, does not exhibit electrochromism. In a more specific embodiment,WO_(x), where x is less than 3.0 and at least about 2.7 is used for theelectrochromic layer. In another embodiment, the electrochromic layer isWOx, where x is between about 2.7 and about 2.9. Techniques such asRutherford Backscattering Spectroscopy (RBS) can identify the totalnumber of oxygen atoms which include those bonded to tungsten and thosenot bonded to tungsten. In some instances, tungsten oxide layers where xis 3 or greater exhibit electrochromism, presumably due to unboundexcess oxygen along with sub-stoichiometric tungsten oxide. In anotherembodiment, the tungsten oxide layer has stoichiometric or greateroxygen, where x is 3.0 to about 3.5.

In certain embodiments, the tungsten oxide is crystalline,nanocrystalline, or amorphous. In some embodiments, the tungsten oxideis substantially nanocrystalline, with grain sizes, on average, fromabout 5 nm to about 50 nm (or from about 5 nm to about 20 nm), ascharacterized by transmission electron microscopy (TEM). The tungstenoxide morphology may also be characterized as nanocrystalline usingx-ray diffraction (XRD). For example, nanocrystalline electrochromictungsten oxide may be characterized by the following XRD features: acrystal size of about 10 nm to about 100 nm (for example, about 55 nm).Further, nanocrystalline tungsten oxide may exhibit limited long rangeorder, for example, on the order of several (about 5 to about 20)tungsten oxide unit cells.

The thickness of the electrochromic layer 506 depends on theelectrochromic material selected for the electrochromic layer. In someembodiments, the electrochromic layer 506 is about 50 nm to 2,000 nm, orabout 200 nm to 700 nm. In some embodiments, the electrochromic layer isabout 300 nm to about 500 nm. The thickness of the electrochromic layer506 is also substantially uniform. In one embodiment, a substantiallyuniform electrochromic layer varies only about ±10% in each of theaforementioned thickness ranges. In another embodiment, a substantiallyuniform electrochromic layer varies only about ±5% in each of theaforementioned thickness ranges. In another embodiment, a substantiallyuniform electrochromic layer varies only about ±3% in each of theaforementioned thickness ranges.

Generally, in electrochromic materials, the colorization (or change inany optical property—for example, absorbance, reflectance, andtransmittance) of the electrochromic material is caused by reversibleion insertion into the material (for example, intercalation) and acorresponding injection of a charge balancing electron. Typically somefraction of the ion responsible for the optical transition isirreversibly bound up in the electrochromic material. As explained belowsome or all of the irreversibly bound ions are used to compensate “blindcharge” in the material. In most electrochromic materials, suitable ionsinclude lithium ions (Li⁺) and hydrogen ions (H⁺) (that is, protons). Insome cases, however, other ions will be suitable. These include, forexample, deuterium ions (D⁺), sodium ions (Na⁺), potassium ions (K⁺),calcium ions (Ca⁺⁺), barium ions (B⁺⁺), strontium ions (Sr⁺⁺), andmagnesium ions (Mg⁺⁺). In various embodiments described herein, lithiumions are used to produce the electrochromic phenomena. Intercalation oflithium ions into tungsten oxide (WO_(3-y) (0<y≦˜0.3)) causes thetungsten oxide to change from transparent (bleached state) to blue(colored state).

Referring again to FIG. 5, in electrochromic stack 520, ion conductinglayer 508 overlays electrochromic layer 506. On top of ion conductinglayer 508 is counter electrode layer 510. In some embodiments, counterelectrode layer 510 is inorganic and/or solid. The counter electrodelayer may comprise one or more of a number of different materials thatare capable of serving as reservoirs of ions when the electrochromicdevice is in the bleached state. During an electrochromic transitioninitiated by, for example, application of an appropriate electricpotential, the counter electrode layer transfers some or all of the ionsit holds to the electrochromic layer, changing the electrochromic layerto the colored state. Concurrently, in the case of NiWO, the counterelectrode layer colors with the loss of ions.

In some embodiments, suitable materials for the counter electrodecomplementary to WO₃ include nickel oxide (NiO), nickel tungsten oxide(NiWO), nickel vanadium oxide, nickel chromium oxide, nickel aluminumoxide, nickel manganese oxide, nickel magnesium oxide, chromium oxide(Cr₂O₃), manganese oxide (MnO₂), Prussian blue. Optically passivecounter electrodes comprise cerium titanium oxide (CeO₂—TiO₂), ceriumzirconium oxide (CeO₂—ZrO₂), nickel oxide (NiO), nickel-tungsten oxide(NiWO), vanadium oxide (V₂O₅), and mixtures of oxides (for example, amixture of Ni₂O₃ and WO₃). Doped formulations of these oxides may alsobe used, with dopants including, for example, tantalum and tungsten.Because counter electrode layer 510 contains the ions used to producethe electrochromic phenomenon in the electrochromic material when theelectrochromic material is in the bleached state, the counter electrodepreferably has high transmittance and a neutral color when it holdssignificant quantities of these ions.

In some embodiments, nickel-tungsten oxide (NiWO) is used in the counterelectrode layer. In certain embodiments, the amount of nickel present inthe nickel-tungsten oxide can be up to about 90% by weight of thenickel-tungsten oxide. In a specific embodiment, the mass ratio ofnickel to tungsten in the nickel-tungsten oxide is between about 4:6 and6:4 (for example, about 1:1). In one embodiment, the NiWO is betweenabout 15% (atomic) Ni and about 60% Ni; between about 10% W and about40% W; and between about 30% O and about 75% O. In another embodiment,the NiWO is between about 30% (atomic) Ni and about 45% Ni; betweenabout 10% W and about 25% W; and between about 35% O and about 50% O. Inone embodiment, the NiWO is about 42% (atomic) Ni, about 14% W, andabout 44% O.

When charge is removed from a counter electrode 510 made of nickeltungsten oxide (that is, ions are transported from the counter electrode510 to the electrochromic layer 506), the counter electrode layer willturn from a transparent state to a brown colored state.

The counter electrode morphology may be crystalline, nanocrystalline, oramorphous. In some embodiments, where the counter electrode layer isnickel-tungsten oxide, the counter electrode material is amorphous orsubstantially amorphous. Substantially amorphous nickel-tungsten oxidecounter electrodes have been found to perform better, under someconditions, in comparison to their crystalline counterparts. Theamorphous state of the nickel-tungsten oxide may be obtained though theuse of certain processing conditions, described below. While not wishingto be bound to any theory or mechanism, it is believed that amorphousnickel-tungsten oxide is produced by relatively higher energy atoms inthe sputtering process. Higher energy atoms are obtained, for example,in a sputtering process with higher target powers, lower chamberpressures (that is, higher vacuum), and smaller source to substratedistances. Under the described process conditions, higher density films,with better stability under UV/heat exposure are produced.

In some embodiments, the thickness of the counter electrode is about 50nm about 650 nm. In some embodiments, the thickness of the counterelectrode is about 100 nm to about 400 nm, preferably in the range ofabout 200 nm to 300 nm. The thickness of the counter electrode layer 510is also substantially uniform. In one embodiment, a substantiallyuniform counter electrode layer varies only about ±10% in each of theaforementioned thickness ranges. In another embodiment, a substantiallyuniform counter electrode layer varies only about ±5% in each of theaforementioned thickness ranges. In another embodiment, a substantiallyuniform counter electrode layer varies only about ±3% in each of theaforementioned thickness ranges.

The amount of ions held in the counter electrode layer during thebleached state (and correspondingly in the electrochromic layer duringthe colored state) and available to drive the electrochromic transitiondepends on the composition of the layers as well as the thickness of thelayers and the fabrication method. Both the electrochromic layer and thecounter electrode layer are capable of supporting available charge (inthe form of lithium ions and electrons) in the neighborhood of severaltens of millicoulombs per square centimeter of layer surface area. Thecharge capacity of an electrochromic film is the amount of charge thatcan be loaded and unloaded reversibly per unit area and unit thicknessof the film by applying an external voltage or potential. In oneembodiment, the WO₃ layer has a charge capacity of between about 30 andabout 150 mC/cm²/micron. In another embodiment, the WO₃ layer has acharge capacity of between about 50 and about 100 mC/cm²/micron. In oneembodiment, the NiWO layer has a charge capacity of between about 75 andabout 200 mC/cm²/micron. In another embodiment, the NiWO layer has acharge capacity of between about 100 and about 150 mC/cm²/micron.

In electrochromic devices with distinct layers, between electrochromiclayer 506 and counter electrode layer 510, there is an ion conductinglayer 508. Ion conducting layer 508 serves as a medium through whichions are transported (in the manner of an electrolyte) when theelectrochromic device transforms between the bleached state and thecolored state. Preferably, ion conducting layer 508 is highly conductiveto the relevant ions for the electrochromic and the counter electrodelayers, but has sufficiently low electron conductivity that negligibleelectron transfer takes place during normal operation. A thin ionconducting layer with high ionic conductivity permits fast ionconduction and hence fast switching for high performance electrochromicdevices. In certain embodiments, the ion conducting layer 508 isinorganic and/or solid. When fabricated from a material and in a mannerthat produces relatively few defects, the ion conductor layer can bemade very thin to produce a high performance device. In variousimplementations, the ion conductor material has an ionic conductivity ofbetween about 10⁸ Siemens/cm or ohm⁻¹ cm⁻¹ and about 10⁹ Siemens/cm orohm⁻¹ cm⁻¹ and an electronic resistance of about 10¹¹ ohms-cm.

Examples of suitable ion conducting layers (for electrochromic deviceshaving a distinct IC layer) include silicates, silicon oxides, tungstenoxides, tantalum oxides, niobium oxides, and borates. The silicon oxidesinclude silicon-aluminum-oxide. These materials may be doped withdifferent dopants, including lithium. Lithium doped silicon oxidesinclude lithium silicon-aluminum-oxide. In some embodiments, the ionconducting layer comprises a silicate-based structure. In otherembodiments, suitable ion conductors particularly adapted for lithiumion transport include, but are not limited to, lithium silicate, lithiumaluminum silicate, lithium aluminum borate, lithium aluminum fluoride,lithium borate, lithium nitride, lithium zirconium silicate, lithiumniobate, lithium borosilicate, lithium phosphosilicate, and other suchlithium-based ceramic materials, silicas, or silicon oxides, includinglithium silicon-oxide. Any material, however, may be used for the ionconducting layer 508 provided it can be fabricated with low defectivityand it allows for the passage of ions between the counter electrodelayer 510 to the electrochromic layer 506 while substantially preventingthe passage of electrons.

In certain embodiments, the ion conducting layer is crystalline,nanocrystalline, or amorphous. Typically, the ion conducting layer isamorphous. In another embodiment, the ion conducting layer isnanocrystalline. In yet another embodiment, the ion conducting layer iscrystalline.

In some embodiments, a silicon-aluminum-oxide (SiAlO) is used for theion conducting layer 508. In a specific embodiment, a silicon/aluminumtarget used to fabricate the ion conductor layer via sputtering containsbetween about 6 and about 20 atomic percent aluminum. This defines theratio of silicon to aluminum in the ion conducting layer. In someembodiments, the silicon-aluminum-oxide ion conducting layer 508 isamorphous.

The thickness of the ion conducting layer 508 may vary depending on thematerial. In some embodiments, the ion conducting layer 508 is about 5nm to 100 nm thick, preferably about 10 nm to 60 nm thick. In someembodiments, the ion conducting layer is about 15 nm to 40 nm thick orabout 25 nm to 30 nm thick. The thickness of the ion conducting layer isalso substantially uniform. In one embodiment, a substantially uniformion conducting layer varies by not more than about ±10% in each of theaforementioned thickness ranges. In another embodiment, a substantiallyuniform ion conducting layer varies by not more than about ±5% in eachof the aforementioned thickness ranges. In another embodiment, asubstantially uniform ion conducting layer varies by not more than about±3% in each of the aforementioned thickness ranges.

Ions transported across the ion conducting layer between theelectrochromic layer and the counter electrode layer serve to effect acolor change in the electrochromic layer (that is, change theelectrochromic device from the bleached state to the colored state).Depending on the choice of materials for the electrochromic devicestack, such ions include lithium ions (Li⁺) and hydrogen ions (H⁺) (thatis, protons). As mentioned above, other ions may be employed in certainembodiments. These include deuterium ions (D⁺), sodium ions (Na⁺),potassium ions (K⁺), calcium ions (Ca⁺⁺), barium ions (Ba⁺⁺), strontiumions (Sr⁺⁺), and magnesium ions (Mg⁺⁺).

As noted, the ion conducting layer 508 should have very few defects.Among other problems, defects in the ion conducting layer may result inshort circuits between the electrochromic layer and the counterelectrode layer (described in more detail below in relation to FIG. 5).A short circuit occurs when electrical communication is establishedbetween oppositely charged conductive layers, for example a conductiveparticle makes contact with each of two conductive and electricallycharged layers (as opposed to a “pin hole” which is a defect which doesnot create a short circuit between oppositely charged conductivelayers). When a short circuit occurs, electrons rather than ions migratebetween the electrochromic layer and the counter electrode, typicallyresulting in bright spots (that is, spots where the window does notswitch but instead, maintains the open circuit coloration which is oftenmuch lighter than the colored state) at the location of the short whenthe electrochromic device is otherwise in the colored state. The ionconducting layer is preferably as thin as possible, without any shortsbetween the electrochromic layer and the counter electrode layer. Asindicated, low defectivity in the ion conducting layer 508 (or elsewherein the electrochromic device) allows for a thinner ion conducting layer508. Ion transport between the electrochromic layer and the counterelectrode layer with electrochemical cycling is faster when using a thinion conducting layer. To generalize, the defectivity criteria specifiedherein may apply to any specific layer (ion conducting layer orotherwise) in the stack or to the stack as a whole or to any portionthereof. Defectivity criteria will be further discussed below.

The electrochromic device 500 may include one or more additional layers(not shown) such as one or more passive layers. Passive layers used toimprove certain optical properties may be included in electrochromicdevice 500. Passive layers for providing moisture or scratch resistancemay also be included in the electrochromic device 500. For example, theconductive layers may be treated with anti-reflective or protectiveoxide or nitride layers. Other passive layers may serve to hermeticallyseal the electrochromic device 500.

FIG. 6A is a schematic cross-section of an electrochromic device in ableached state (or transitioning to a bleached state). In accordancewith specific embodiments, the electrochromic device 600 includes atungsten oxide electrochromic layer (EC) 606 and a nickel-tungsten oxidecounter electrode layer (CE) 610. In some cases, the tungsten oxideelectrochromic layer 606 has a nanocrystalline, or substantiallynanocrystalline, morphology. In some embodiments, the nickel-tungstenoxide counter electrode layer 610 has an amorphous, or substantiallyamorphous, morphology. In some embodiments, the weight percent ratio oftungsten to nickel in the nickel-tungsten oxide is about 0.40-0.60

The electrochromic device 600 also includes substrate 602, conductivelayer (CL) 604, ion conducting layer (IC) 608, and conductive layer (CL)614. In some embodiments, the substrate 602 and conductive layer 604together comprise a TEC-Glass™. As indicated, the electrochromic devicesdescribed herein, such as those of FIG. 6A, often find beneficialapplication in architectural glass. Thus, in some embodiments, thesubstrate 602 is of the dimensions such that it may be classified asarchitectural glass. In some embodiments, the conductive layer 614 isindium tin oxide (ITO). In some embodiments, the ion conducting layer608 is a silicon-aluminum-oxide.

The voltage source 616 is configured to apply a potential toelectrochromic stack 620 through suitable connections (for example, busbars) to conductive layers 604 and 614. In some embodiments, the voltagesource is configured to apply a potential of about 2 volts in order todrive a transition of the device from one optical state to another. Thepolarity of the potential as shown in FIG. 6A is such that the ions(lithium ions in this example) primarily reside (as indicated by thedashed arrow) in nickel-tungsten oxide counter electrode layer 610.

In embodiments employing tungsten oxide as the electrochromic layer andnickel-tungsten oxide as the counter electrode layer, the ratio of theelectrochromic layer thickness to the counter electrode layer thicknessmay be about 1.7:1 to 2.3:1 (for example, about 2:1). In someembodiments, the electrochromic tungsten oxide layer is about 200 nm to700 nm thick. In further embodiments, the electrochromic tungsten oxidelayer is about 400 nm to 500 nm thick. In some embodiments, thenickel-tungsten oxide counter electrode layer is about 100 nm to 350 nmthick. In further embodiments, and the nickel-tungsten oxide counterelectrode layer is about 200 nm to 250 nm thick. In yet furtherembodiments, the nickel-tungsten oxide counter electrode layer is about240 nm thick. Also, in some embodiments, the silicon-aluminum-oxide ionconducting layer 608 is about 10 nm to 100 nm thick. In furtherembodiments, the silicon-aluminum-oxide ion conducting layer is about 20nm to 50 nm thick.

As indicated above, electrochromic materials may contain blind charge.The blind charge in an electrochromic material is the charge (forexample, negative charge in the cases of tungsten oxide electrochromicmaterial) that exists in the material as fabricated, absent compensationby oppositely charged ions or other charge carriers. With tungstenoxide, for example, the magnitude of the blind charge depends upon theexcess oxygen concentration during sputtering of the tungsten oxide.Functionally, blind charge must be compensated before the ions employedto transform the electrochromic material can effectively change anoptical property of the electrochromic material. Without priorcompensation of the blind charge, ions supplied to an electrochromicmaterial will irreversibly incorporate in the material and have noeffect on the optical state of the material. Thus, an electrochromicdevice is typically provided with ions, such as lithium ions or protons,in an amount sufficient both to compensate the blind charge and toprovide a supply of ions for reversibly switching the electrochromicmaterial between two optical states. In many known electrochromicdevices, charge is lost during the first electrochemical cycle incompensating blind charge.

In some embodiments, lithium is present in the electrochromic stack 620in an amount sufficient to compensate the blind charge in theelectrochromic layer 606 and then an additional amount of about 1.5 to2.5 times the amount used to compensate the blind charge (by mass) inthe stack (initially in the counter electrode layer 610 for example).That is, there is about 1.5 to 2.5 times the amount of lithium needed tocompensate the blind charge that is provided for reversible cyclingbetween the electrochromic layer 606 and the counter electrode layer 610in the electrochromic stack 620. In some embodiments, there are enoughlithium in the electrochromic stack 620 to compensate the blind chargein the electrochromic layer 606 and then about two times this amount (bymass) in the counter electrode layer 610 or elsewhere in the stack.

FIG. 6B is a schematic cross-section of electrochromic device 600 shownin FIG. 6A but in a colored state (or transitioning to a colored state).In FIG. 6B, the polarity of voltage source 616 is reversed, so that theelectrochromic layer is made more negative to accept additional lithiumions, and thereby transition to the colored state. As indicated by thedashed arrow, lithium ions are transported across the ion conductinglayer 608 to the tungsten oxide electrochromic layer 606. The tungstenoxide electrochromic layer 606 is shown in the colored state. Thenickel-tungsten oxide counter electrode 610 is also shown in the coloredstate. As explained, nickel-tungsten oxide becomes progressively moreopaque as it gives up (deintercalates) lithium ions. In this example,there is a synergistic effect where the transition to colored states forboth layers 606 and 610 are additive toward reducing the amount of lighttransmitted through the stack and substrate.

The all solid state and inorganic electrochromic devices described abovehave low defectivity and high reliability, and thus are particularlywell suited for embodiments described herein. Other low defectivity allsolid state and inorganic electrochromic devices are described below.

Low-Defectivity Solid State and Inorganic Electrochromic Devices withouta Distinct IC Layer

As described above, an electrochromic device typically includes anelectrochromic (“EC”) electrode layer and a counter electrode (“CE”)layer, separated by an ionically conductive (“IC”) layer that is highlyconductive to ions and highly resistive to electrons. As conventionallyunderstood, the ionically conductive layer therefore prevents shortingbetween the electrochromic layer and the counter electrode layer. Theionically conductive layer allows the electrochromic and counterelectrodes to hold a charge and thereby maintain their bleached orcolored states. In electrochromic devices having distinct layers, thecomponents form a stack which includes the ion conducting layersandwiched between the electrochromic electrode layer and the counterelectrode layer. The boundaries between these three stack components aredefined by abrupt changes in composition and/or microstructure. Thus,the devices have three distinct layers with two abrupt interfaces.

Quite surprisingly, it has been discovered that high qualityelectrochromic devices can be fabricated without depositing an ionicallyconducting electrically insulating layer. In accordance with certainembodiments, the counter electrode and electrochromic electrodes areformed immediately adjacent one another, often in direct contact,without separately depositing an ionically conducting layer. It isbelieved that various fabrication processes and/or physical or chemicalmechanisms produce an interfacial region between contactingelectrochromic and counter electrode layers, and that this interfacialregion serves at least some functions of an ionically conductiveelectronically insulating layer in devices having such a distinct layer.

In some embodiments, such electrochromic devices having an ionconducting electronically insulating interfacial region rather than adistinct IC layer are employed in one or more panes of multi-pane windowunits described herein. Such devices, and methods of fabricating them,are described in U.S. patent application Ser. Nos. 12/772,055 and12/772,075, each filed on Apr. 30, 2010, and in U.S. patent applicationSer. Nos. 12/814,277 and 12/814,279, each filed on Jun. 11, 2010—each ofthe four applications is entitled “Electrochromic Devices,” each namesZhongchun Wang et al. as inventors, and each is incorporated byreference herein for all purposes. These electrochromic devices can alsobe made with low defectivity and thus are particularly well suited formulti-pane window units described herein. A brief description of thesedevices follows.

FIG. 7 is a schematic cross-section of an electrochromic device, 500, ina colored state, where the device has an ion conducting electronicallyinsulating interfacial region, 708, serving the function of a distinctIC layer. Voltage source 616, conductive layers 614 and 604, andsubstrate 602 are essentially the same as described in relation to FIGS.6A and 6B. Between conductive layers 614 and 604 is a region 710, whichincludes counter electrode layer 610, electrochromic layer 606 and anion conducting electronically insulating interfacial region, 708,between them, rather than a distinct IC layer. In this example, there isno distinct boundary between counter electrode layer 610 and interfacialregion 708, nor is there a distinct boundary between electrochromiclayer 606 and interfacial region 708. Rather, there is a diffusetransition between CE layer 610 and interfacial region 708, and betweeninterfacial region 708 and EC layer 606. Conventional wisdom was thateach of the three layers should be laid down as distinct, uniformlydeposited and smooth layers to form a stack. The interface between eachlayer should be “clean” where there is little intermixing of materialsfrom each layer at the interface. One of ordinary skill in the art wouldrecognize that in a practical sense there is inevitably some degree ofmaterial mixing at layer interfaces, but the point is, in conventionalfabrication methods any such mixing is unintentional and minimal. Theinventors have found that interfacial regions serving as IC layers canbe formed where the interfacial region includes significant quantitiesof one or more electrochromic and/or counter electrode materials bydesign. This is a radical departure from conventional fabricationmethods. These all solid state and inorganic electrochromic devices alsohave low defectivity and reliability, and thus are particularly wellsuited for embodiments described herein.

Visual Defects in Electrochromic Devices

As indicated above, virtually any electrochromic device will work withthe multi-pane window units described herein, by virtue of the fact thatvisual defects in overlapping devices, for example one each on two panesof a dual-pane window unit, are negated by the low probability that thedefects will align sufficiently for the user to actually see them whenboth panes of the window are darkened. The electrochromic devices asdescribed above have a reduced number of defects; that is, considerablyfewer than are present in comparable prior devices, therefore they areparticularly well suited for the embodiments described.

As used herein, the term “defect” refers to a defective point or regionof an electrochromic device. Defects may be caused by electrical shortsor by pinholes. Further, defects may be characterized as visible ornon-visible. Often a defect will be manifest as visually discernableanomalies in the electrochromic window or other device. Such defects arereferred to herein as “visible” defects. Other defects are so small thatthey are not visually noticeable to the observer in normal use (forexample, such defects do not produce a noticeable light point when thedevice is in the colored state during daytime). A “short” is a localizedelectronically conductive pathway spanning the ion conducting layer (forexample, an electronically conductive pathway between the two TCOlayers). A “pinhole” is a region where one or more layers of theelectrochromic device are missing or damaged so that electrochromism isnot exhibited. Pinholes are not electrical shorts. Three types ofdefects are of primary concern: (1) visible pinholes, (2) visibleshorts, and (3) non-visible shorts. Typically, though not necessarily, avisible short will have a defect dimension of at least about 3micrometers resulting in a region, for example of about 1 cm indiameter, where the electrochromic effect is perceptiblydiminished—these regions can be reduced significantly by isolating thedefect, for example circumscribing the defect via laser scribe, causingthe visible short so that to the naked eye the visible short willresemble only a visible pinhole. A visible pinhole will have a defectdimension of at least about 100 micrometers, thus is much harder todiscern visually than a visible short. One aspect of the invention is toreduce, if not eliminate, the number of visual defects the end useractually observes.

In some cases, an electrical short is created by a conductive particlelodging in the ion conducting layer, thereby causing an electronic pathbetween the counter electrode layer and the electrochromic layer or theTCO associated with either one of them. In some other cases, a defect iscaused by a particle on the substrate (on which the electrochromic stackis fabricated) and such particle causes layer delamination (sometimescalled “pop-off”) or the layers not to adhere to the substrate. Bothtypes of defects are illustrated below in FIGS. 5 and 6A-6C. Adelamination or pop-off defect can lead to a short if it occurs before aTCO or associated EC or CE is deposited. In such cases, the subsequentlydeposited TCO or EC/CE layer will directly contact an underlying TCO orCE/EC layer providing direct electronic conductive pathway. A fewexamples of defect sources are presented in Table 2 below. Table 2 isintended to provide examples of mechanisms that lead to the differenttypes of visible and non-visible defects. Additional factors exist whichmay influence how the EC window responds to a defect within the stack.

An electrical short, even a non-visible one, can cause leakage currentacross the ion conducting layer and result in a potential drop in thevicinity of the short. If the potential drop is of sufficient magnitudeit will prevent the electrochromic device from undergoing anelectrochromic transition in the vicinity of the short. In the case of avisible short the defect will appear as a light central region (when thedevice is in the colored state) with a diffuse boundary such that thedevice gradually darkens with distance from the center of the short. Ifthere are a significant number of electrical shorts (visible ornon-visible) concentrated in an area of an electrochromic device, theymay collectively impact a broad region of the device whereby the devicecannot switch in such region. This is because the potential differencebetween the EC and CE layers in such regions cannot attain a thresholdlevel required to drive ions across the ion conductive layer.

TABLE 2 Particle Location Worst Case Failure Effect float pops offleaving pinhole pinhole TEC pops off - ITO-TEC short visible shortvoltage drop EC leakage across IC visible short voltage drop IC pops offleaving pinhole pinhole CE pops off leaving pinhole pinhole

In certain implementations described herein, the shorts (both visibleand non-visible) are sufficiently well controlled that the leakagecurrent does not have this effect anywhere on the device. It should beunderstood that leakage current may result from sources other thanshort-type defects. Such other sources include broad-based leakageacross the ion conducting layer and edge defects such as roll offdefects as described elsewhere herein and scribe line defects. Theemphasis here is on leakage caused only by points of electrical shortingacross the ion conducting layer (or interfacial region) in the interiorregions of the electrochromic device. It should be noted, however, thatelectrochromic devices employing interfacial regions serving as IClayers, as described above, can have higher than conventionally acceptedleakage currents but the devices show good performance nonetheless.However, visual defects do still occur in these electrochromic devices.

FIG. 8 is a schematic cross-section of an electrochromic device 800 witha particle in the ion conducting layer causing a localized defect in thedevice. Device 800 is depicted with typical distinct layers, althoughparticles in this size regime would cause visual defects inelectrochromic devices employing ion conducting electronicallyinsulating interfacial regions as well. Electrochromic device 800includes the same components as depicted in FIG. 6A for electrochromicdevice 600. In the ion conducting layer 608 of electrochromic device800, however, there is a conductive particle 802 or other artifactcausing a defect. Conductive particle 802 results in a short betweenelectrochromic layer 606 and counter electrode layer 610. This shortdoes not allow the flow of ions between electrochromic layer 606 andcounter electrode layer 610, instead allowing electrons to pass locallybetween the layers, resulting in a transparent region 804 in theelectrochromic layer 606 and a transparent region 806 in the counterelectrode layer 610 when the remainder of layers 610 and 606 are in thecolored state. That is, if electrochromic device 800 is in the coloredstate, conductive particle 802 renders regions 804 and 806 of theelectrochromic device unable to enter into the colored state. Thesedefect regions are sometimes referred to as “constellations” becausethey appear as a series of bright spots (or stars) against a darkbackground (the remainder of the device being in the colored state).Humans will naturally direct their attention to the constellations andoften find them distracting or unattractive.

FIG. 9A is a schematic cross-section of an electrochromic device 900with a particle 902 or other debris on conductive layer 604 prior todepositing the remainder of the electrochromic stack. Electrochromicdevice 900 includes the same components as electrochromic device 600.Particle 902 causes the layers in the electrochromic stack 620 to bulgein the region of particle 902, due to conformal layers 606-610 beingdeposited sequentially over particle 902 as depicted (in this example,layer 614 has not yet been deposited). While not wishing to be bound bya particular theory, it is believed that layering over such particles,given the relatively thin nature of the layers, can cause stress in thearea where the bulges are formed. More particularly, in each layer,around the perimeter of the bulged region, there can be defects in thelayer, for example in the lattice arrangement or on a more macroscopiclevel, cracks or voids. One consequence of these defects would be, forexample, an electrical short between electrochromic layer 606 andcounter electrode layer 610 or loss of ion conductivity in layer 608.These defects are not depicted in FIG. 9A, however.

Referring to FIG. 9B, another consequence of defects caused by particle902 is called a “pop-off.” In this example, prior to deposition ofconductive layer 614, a portion above the conductive layer 604 in theregion of particle 902 breaks loose, carrying with it portions ofelectrochromic layer 606, ion conducting layer 608, and counterelectrode layer 610. The “pop-off” is piece 904, which includes particle902, a portion of electrochromic layer 606, as well as ion conductinglayer 608 and counter electrode layer 610. The result is an exposed areaof conductive layer 604. Referring to FIG. 9C, after pop-off and onceconductive layer 614 is deposited, an electrical short is formed whereconductive layer 614 comes in contact with conductive layer 604. Thiselectrical short would leave a transparent region in electrochromicdevice 900 when it is in the colored state, similar in appearance to thedefect created by the short described above in relation to FIG. 8.

Pop-off defects due to particles or debris on substrate 602 or 604 (asdescribed above), on ion conducting layer 608, and on counter electrodelayer 610 may also occur, causing pinhole defects when theelectrochromic device is in the colored state.

The net result of the aforementioned defects are that constellations,electrical shorts and other defects result in pinholes, even after, forexample, laser scribing used to isolate and minimize such defects. So,it is desirable to use low-defectivity electrochromic devices in orderto reduce the overall number of pinholes that do exist after mitigationefforts. Below is a brief description of integrated systems formanufacturing such low-defectivity all solid state and inorganicelectrochromic devices on architectural-scale substrates.

Low-Defectivity Electrochromic Devices

The electrochromic devices described above can be manufactured in anintegrated deposition system, for example, on architectural glass. Theelectrochromic devices are used to make window units, for example IGU's,which in turn are used to make electrochromic windows. The term“integrated deposition system” means an apparatus for fabricatingelectrochromic devices on optically transparent and translucentsubstrates. The apparatus has multiple stations, each devoted to aparticular unit operation such as depositing a particular component (orportion of a component) of an electrochromic device, as well ascleaning, etching, and temperature control of such device or portionthereof. The multiple stations are fully integrated such that asubstrate on which an electrochromic device is being fabricated can passfrom one station to the next without being exposed to an externalenvironment. Integrated deposition systems operate with a controlledambient environment inside the system where the process stations arelocated. An exemplary integrated deposition system is described inrelation to FIG. 9.

FIG. 10, depicts in perspective schematic fashion an integrateddeposition system 1000 in accordance with certain embodiments. In thisexample, system 1000 includes an entry load lock, 1002, for introducingthe substrate to the system, and an exit load lock, 1004, for removal ofthe substrate from the system. The load locks allow substrates to beintroduced and removed from the system without disturbing the controlledambient environment of the system. Integrated deposition system 1000 hasa module, 1006, with a plurality of deposition stations to deposit thevarious layers of the electrochromic stack, for example those describedabove. Individual stations within an integrated deposition systems cancontain heaters, coolers, various sputter targets and means to movethem, RF and/or DC power sources and power delivery mechanisms, etchingtools for example plasma etch, gas sources, vacuum sources, glowdischarge sources, process parameter monitors and sensors, robotics,power supplies, and the like.

There is an entry port, 1010, for loading, for example, architecturalglass substrate 1025 (load lock 1004 has a corresponding exit port).Substrate 1025 is supported by a pallet, 1020, which travels along atrack, 1015. Pallet 1020 can translate (as indicated by the doubleheaded arrow) forward and/or backward through system 1000 as may bedesired for one or more deposition processes. In this example, pallet1020 and substrate 1025 are in a substantially vertical orientation. Asubstantially vertical orientation helps to prevent defects becauseparticulate matter that may be generated, for example, fromagglomeration of atoms from sputtering, will tend to succumb to gravityand therefore not deposit on substrate 1025. Also, because architecturalglass substrates tend to be large, a vertical orientation of thesubstrate as it traverses the stations of the integrated depositionsystem enables coating of thinner glass substrates since there are lessconcerns over sag that occurs with thicker hot glass.

Target 1030, in this case a cylindrical target, is orientedsubstantially parallel to and in front of the substrate surface wheredeposition is to take place (for convenience, other sputter means arenot depicted here). Substrate 1025 can translate past target 1030 duringdeposition and/or target 1030 can move in front of substrate 1025.

Integrated deposition system 1000 also has various vacuum pumps, gasinlets, pressure sensors and the like that establish and maintain acontrolled ambient environment within the system. These components arenot shown, but rather would be appreciated by one of ordinary skill inthe art. System 1000 is controlled, for example, via a computer systemor other controller, represented in FIG. 10 by an LCD and keyboard,1035. One of ordinary skill in the art would appreciate that embodimentsof the present invention may employ various processes involving datastored in or transferred through one or more computer systems. Thecontrol apparatus may be specially constructed for the requiredpurposes, or it may be a general-purpose computer selectively activatedor reconfigured by a computer program and/or data structure stored inthe computer.

By using such an integrated deposition system, electrochromic devices ofvery low defectivity can be produced. In one embodiment, the number ofvisible pinhole defects in a single electrochromic device is no greaterthan about 0.04 per square centimeter. In another embodiment, the numberof visible pinhole defects in a single electrochromic device is nogreater than about 0.02 per square centimeter, and in more specificembodiments, the number of such defects is no greater than about 0.01per square centimeter.

As mentioned, typically, the visible short-type defects are individuallytreated after fabrication, for example laser scribed to isolate them, toleave short-related pinholes as the only visible defects. In oneembodiment, the number of visible short related pinhole defects in asingle electrochromic device is no greater than about 0.005 per squarecentimeter. In another embodiment, the number of visible short-relatedpinhole defects in a single electrochromic device is no greater thanabout 0.003 per square centimeter, and in more specific embodiments, thenumber of such defects is no greater than about 0.001 per squarecentimeter. In one embodiment, the total number of visible defects,pinholes and short-related pinholes created from isolating visibleshort-related defects in a single device, is less than about 0.1 defectsper square centimeter, in another embodiment less than about 0.08defects per square centimeter, in another embodiment less than about0.045 defects per square centimeter (less than about 450 defects persquare meter of window).

In conventional electrochromic windows, one pane of electrochromic glassis integrated into an IGU. An IGU includes multiple glass panesassembled into a unit, generally with the intention of maximizing thethermal insulating properties of a gas contained in the space formed bythe unit while at the same time providing clear vision through the unit.Insulating glass units incorporating electrochromic glass would besimilar to IGU's currently known in the art, except for electrical leadsfor connecting the electrochromic glass to voltage source. Due to thehigher temperatures (due to absorption of radiant energy by anelectrochromic glass) that electrochromic IGU's may experience, morerobust sealants than those used in conventional IGU's may be necessary.For example, stainless steel spacer bars, high temperaturepolyisobutylene (PIB), new secondary sealants, foil coated PIB tape forspacer bar seams, and the like.

Although the electrochromic devices described above have very lowdefectivity, there are still visible defects. And since conventionallyan IGU includes only one pane of glass which has an electrochromicdevice, even if such an IGU included the low defectivity devices, atleast a small number of defects would still be apparent when the windowis in the colored state.

Although the foregoing invention has been described in some detail tofacilitate understanding, the described embodiments are to be consideredillustrative and not limiting. It will be apparent to one of ordinaryskill in the art that certain changes and modifications can be practicedwithin the scope of the appended claims.

What is claimed is:
 1. A window unit comprising: a first substantiallytransparent substrate and a first electrochromic device disposedthereon; a second substantially transparent substrate and a secondelectrochromic device disposed thereon; and a sealing separator betweenthe first and second substantially transparent substrates, which sealingseparator defines, together with the first and second substantiallytransparent substrates, an interior region that is thermally insulating.2. The window unit of claim 1, wherein the first and secondsubstantially transparent substrates are substantially rigid.
 3. Thewindow unit of claim 1, wherein at least one of the first and secondsubstantially transparent substrates comprises architectural glass. 4.The window unit of claim 1, wherein at least one of the first and secondsubstantially transparent substrates further comprises a low emissivitycoating.
 5. The window unit of claim 1, wherein at least one of thefirst and second electrochromic devices faces the interior region. 6.The window unit of claim 5, wherein both the first and secondelectrochromic devices face the interior region.
 7. The window unit ofclaim 1, wherein the first electrochromic device extends oversubstantially the entire viewable region of the first substantiallytransparent substrate.
 8. The window unit of claim 1, wherein at leastone of the first and second electrochromic devices is a two-stateelectrochromic device.
 9. The window unit of claim 8, wherein both ofthe first and second electrochromic devices are two-state electrochromicdevices and the window unit has two optical states.
 10. The window unitof claim 8, wherein both of the first and second electrochromic devicesare two-state electrochromic devices and the window unit has fouroptical states.
 11. The window unit of claim 10, configured such that,when mounted, the first substantially transparent substrate will faceoutside a room or building and the second substantially transparentsubstrate will face inside said room or building, and wherein each ofthe first and second electrochromic devices has its own hightransmissive state and low transmissive state, and wherein thetransmittance of the second electrochromic device's low transmissivestate is higher than the transmittance of the first electrochromicdevice's low transmissive state.
 12. The window unit of claim 11,wherein the first electrochromic device is better able to withstandenvironmental degradation than the second electrochromic device.
 13. Thewindow unit of claim 11, wherein both the first and secondelectrochromic devices face the interior region.
 14. The window unit ofclaim 12, wherein the second substantially transparent substrate isthinner than the first substantially transparent substrate.
 15. Thewindow unit of claim 1, wherein at least one of the first and secondelectrochromic devices is an entirely solid state and inorganic device.16. The window unit of claim 1, wherein at least one transparentconductive oxide layer of the first and/or the second electrochromicdevices is configured to be heated independently of operation of theelectrochromic device of which it is a component.
 17. The window unit ofclaim 11, wherein the transmittance of the first electrochromic device'slow transmissive state is between about 5% and about 15%, and the firstelectrochromic devices' high transmissive state is between about 75% andabout 95%; and the transmittance of the second electrochromic device'slow transmissive state is between about 20% and about 30%, and thesecond electrochromic devices' high transmissive state is between about75% and about 95%.
 18. The window unit of claim 10, wherein the fouroptical states are: i) overall transmittance of between about 60% andabout 90%; ii) overall transmittance of between about 15% and about 30%;iii) overall transmittance of between about 5% and about 10%; and iv)overall transmittance of between about 0.1% and about 5%.
 19. The windowunit of claim 1, wherein the sealing separator is disposed aboutperipheral regions of the first and second substantially transparentsubstrates without substantially obscuring a viewable region of thewindow unit.
 20. The window unit of claim 1, wherein the sealingseparator hermetically seals the interior region.
 21. The window unit ofclaim 1, wherein the interior region is substantially liquid andmoisture free.
 22. The window unit of claim 1, wherein the interiorregion contains an inert gas.
 23. The window unit of claim 3, whereinboth of the first and second substantially transparent substrates arearchitectural glass.
 24. The window unit of claim 14, wherein the totalnumber of visible defects, pinholes and short-related pinholes createdfrom isolating visible short-related defects in the entirely solid stateand inorganic device is less than about 0.1 defects per squarecentimeter.
 25. The window unit of claim 15, wherein the total number ofvisible defects, pinholes and short-related pinholes created fromisolating visible short-related defects in the entirely solid state andinorganic device is less than about 0.045 defects per square centimeter.26. The window unit of claim 1, wherein the window unit hassubstantially no visible defects.
 27. A method of fabricating a windowunit, the method comprising: arranging, substantially parallel to eachother, a first substantially transparent substrate with a firstelectrochromic device disposed thereon and a second substantiallytransparent substrate with a second electrochromic device disposedthereon; and installing a sealing separator between the first and secondsubstantially transparent substrates, which sealing separator defines,together with the first and second substantially transparent substrates,an interior region, said interior region thermally insulating.
 28. Themethod of claim 27, wherein at least one of the first and secondsubstantially transparent substrates comprises architectural glass. 29.The method of claim 27, wherein at least one of the first and secondsubstantially transparent substrates further comprises a low emissivitycoating.
 30. The method of claim 27, wherein both the first and secondelectrochromic devices face the interior region.
 31. The method of claim27, wherein at least one of the first and second electrochromic devicesis a two-state electrochromic device.
 32. The method of claim 31,wherein both of the first and second electrochromic devices aretwo-state electrochromic devices and the window unit has four opticalstates.
 33. The method of claim 27, wherein at least one of the firstand second electrochromic devices is an entirely solid state andinorganic device.
 34. The method of claim 31, wherein the transmittanceof the first electrochromic device's low transmissive state is betweenabout 5% and about 15%, and the first electrochromic devices' hightransmissive state is between about 75% and about 95%; and thetransmittance of the second electrochromic device's low transmissivestate is between about 20% and about 30%, and the second electrochromicdevices' high transmissive state is between about 75% and about 95%. 35.The method of claim 32, wherein the four optical states are: i) overalltransmittance of between about 60% and about 90%; ii) overalltransmittance of between about 15% and about 30%; iii) overalltransmittance of between about 5% and about 10%; and iv) overalltransmittance of between about 0.1% and about 5%.
 36. The method ofclaim 27, wherein the sealing separator hermetically seals the interiorregion.
 37. The method of claim 27, wherein the interior region containsan inert gas.
 38. The method of claim 27, wherein the window unit has novisible defects.
 39. The method of claim 27, wherein the window unit isan insulating glass unit.
 40. The method of claim 33, wherein the totalnumber of visible defects, pinholes and short-related pinholes createdfrom isolating visible short-related defects in the entirely solid stateand inorganic device is less than about 0.1 defects per squarecentimeter.
 41. The method of claim 33, wherein the total number ofvisible defects, pinholes and short-related pinholes created fromisolating visible short-related defects in the entirely solid state andinorganic device is less than about 0.045 defects per square centimeter.42. A window unit comprising: a first substantially transparentsubstrate and an electrochromic device disposed thereon; a secondsubstantially transparent substrate and a heatable transparentconductive oxide layer thereon; and a sealing separator between thefirst and second substantially transparent substrates, which sealingseparator defines, together with the first and second substantiallytransparent substrates, an interior region that is thermally insulating.43. The window unit of claim 42, wherein the electrochromic device andthe heatable transparent conductive oxide are both in the interiorregion.
 44. The window unit of claim 43, wherein the secondsubstantially transparent substrate comprises an infrared reflectiveand/or infrared absorbing coating.
 45. The window unit of claim 43,wherein the electrochromic device is all solid state and inorganic.